For example, for affixing a silicon oxide film by means of a water oxidation method in semiconductor manufacturing, continuous supply of ultra-high purity water is required. Consequently, the inventors of the present invention have developed a moisture-generating reactor as shown in FIG. 3 and disclosed it (see TOKU-KAI No. 2000-169109 and others).
The moisture-generating reactor is made by welding together reactor body parts 22, 23 which are placed opposite to each other so that a reactor body having a reaction space P inside is formed. The reactor body is provided with a material gas inlet 24, a moisture gas outlet 25, an inlet side reflector 26, an outlet side reflector 27 and others, and has a platinum coating catalyst layer 28 on the inner wall surface of the reactor body part 23 on the side opposite to the material gas inlet 24.
More specifically, the afore-mentioned platinum coating catalyst layer 28 is formed on the whole area of the inner surface of the reactor body part 23 made of SUS316L on the side of the moisture gas outlet 25. After a TiN-made barrier film 28a has been formed on the inner surface of the reaction body part 23, a platinum film 28b is formed thereon.
The thickness of the afore-mentioned barrier film 28a is most preferably 0.1 μm to 5 μm. In the figure, the TiN barrier film 28a with a thickness of about 5 μm is formed with an ion plating method.
Furthermore, a thickness of the afore-mentioned platinum film 28b is preferably 0.1 μm to 3 μm, and in the figure, the platinum film 28b of about 3 μm thick is formed by the vacuum vapor deposition method.
As methods to form the barrier film 28a, in addition to the afore-mentioned ion plating method, it is possible to employ an ion sputtering method, a PVD method such a vacuum vapor deposition method and the like, a chemical vapor deposition method (CVD method), a hot press method, a flame spray method and the like. As methods to form the platinum film 28b, in addition to the afore-mentioned vacuum vapor deposition method, it is possible to employ an ion plating method, an ion sputtering method, a chemical vapor deposition method, a hot press method and the like. In addition, if the barrier film 28a is made of an electrically conductive material such as TiN and the like, a plating method may be employed too.
The afore-mentioned barrier film 28a is formed to prevent the lowering of the reaction rate of the platinum film 28b occurring with the passage of time.
Namely, as the temperature of a stainless steel base material rises due to the reaction heat at the time of generating moisture, Ni and Fe diffuse from the metal base material to the inside of the platinum film 28b. Ni and Fe as diffused are oxidized on the platinum film 28b in an oxidation atmosphere, thus making the platinum film 28b lose its catalytic activity.
To prevent Fe and Ni from diffusing from the metal base material into the platinum film 28b, the afore-mentioned barrier film 28a is formed on the surface of the stainless steel (base material).
For the afore-mentioned barrier film 28a, materials not containing the elements such as Ni and Fe, and not producing oxides in the platinum coating film are most preferred. It has been found that in addition to the afore-mentioned TiN, not only TiAlN, TiC, TiCN and Al2O3 but also oxides and nitrides such as Cr2O3, SiO2, SrN and the like may be used for the barrier film 28a. 
Referring to FIG. 3, hydrogen and oxygen supplied through the material gas inlet 24 into the reactor body are diffused by a diffusing member comprising an inlet side reflector 26 and an outlet side reflector 27, and brought into contact with the platinum coating catalyst layer 28. When hydrogen and oxygen are brought into contact with the platinum coating catalyst layer 28, reactivity of hydrogen and oxygen is raised due to the catalytic action of the platinum such that hydrogen and oxygen are brought in a so-called radicalized state. The radicalized hydrogen and oxygen instantly react at the temperature (about 300° C.˜400° C.) lower than the combustion temperature of a hydrogen mixture gas such that moisture is produced without the high temperature combustion.
Generated moisture (moisture gas) is guided outside through the moisture gas outlet 25 and supplied to a semiconductor manufacturing chamber and the like (not illustrated).